I. Field of the Invention
This invention relates to an apparatus for automatically and continuously analyzing a liquid sample and more particularly to a liquid-analyzing apparatus equipped with a device designed continuously to pass a liquid sample through a tube included in the apparatus characteristically in the form divided into batches each having a prescribed quantity by interposing a preset amount of gas between the adjacent batches of said liquid sample.
II. Description of Prior Art
Generally, devices for automatic chemical analysis of a liquid sample are broadly classified into the discrete and continuous flow types. The discrete type required a considerable amount of a liquid sample and liquid reagent to be used for each analytic operation, through it did not pose any problem in respect to construction. Further, the discrete type analytic apparatus had the drawbacks that upon completion of each analysis, the interior contamination of said apparatus caused by the preceding sample had to be cleaned off, before the succeeding one was analyzed; said cleaning was a troublesome work consuming much the same length of time as analysis itself; where numerous kinds of sample were analyzed by the above-mentioned discrete type apparatus, the analytic work even required a longer time than when as many kinds of sample were manually analyzed; and elimination of the interior contamination of the apparatus was not actually carried out so satisfactorily as it should be, resulting in a gradual decline in the precision of analysis, where the apparatus was used at a close interval.
A continuous flow type analytic apparatus improved on the above-mentioned discrete type is set forth, for example, in the U.S. Pat. No. 2,899,280. With said United States patent, an elastic tube is squeezed, for example, by a proportioning pump, giving rise to the continuous flow of a sample or any other liquid. Air introduced by the proportioning pump through another elastic tube branching from the first mentioned elastic tube is forcefully carried into the liquid running through the first mentioned tube. Thus alternate series of batches of liquid sample and the air respectively having a prescribed quantity run through that portion of a main tube which follows the converging point of both liquid and air tubes. The batches of the liquid sample are successively analyzed by an analyzer positioned ahead of the mixed streams of liquid and air. As the mixed streams flow onward through the main tube, the batches of air included in the mixed streams clean off the internal contamination of the main tube caused by the preceding batches of liquid sample. With such an apparatus as disclosed in said United States Patent, the cleaning effect of the air batches enables analysis to be carried out with few errors even when said apparatus is repeatedly operated to analyze one kind of sample after another at a close interval. Though it indeed has a prominent power of analyzing numerous kinds of sample with high precision, yet the analytic apparatus such as disclosed in the above-mentioned United States Patent still has the drawbacks that the flow rates of a liquid sample and air which jointly act to define the quantity of the batches of the liquid should be very closely controlled and also are limited by the pressure applied by a pump and the inner diameter of the elastic tubes of the liquid and air; the elastic tubes of the liquid and air which are frequently squeezed by the pump are subject to wear and eventually to breakage during a long period of use; and, when the inner walls of said tubes are exposed to organic solvents, strong acids or strong alkalis, particularly at a high temperature, the tubes as a whole are corroded or become brittle to remain resilient, resulting in the failure to maintain the quantities of the batches of the liquid and air at prescribed levels.